1. Field of the Invention
This invention relates to brake calipers for use with disc brakes. In particular, this invention relates to the mounting arrangement of brake calipers to a vehicle support element.
2. Discussion of Related Art
In typical disc brake assemblies, a rotor is mounted on a wheel hub for rotation. One or more pairs of brake pads, generally designed as friction material carried on a backing plate, are supported on either side of the rotor by a caliper or an anchor bracket. Calipers are designed to apply the braking force by moving a piston relative to the rotor to thereby move the brake pad into and out of contact with the rotor. The pistons are supported in a bore in the caliper and abut the backing plate of the brake pad to move the brake pad toward the rotor upon application of a braking force. The caliper can be hydraulically actuated, for example, to selectively press the brake pads against the surface of the rotor to stop the rotation of the rotor, and hence the wheel hub, by forcing hydraulic brake fluid into the piston bore.
A fixed type caliper is rigidly mounted to a fixed mounting member of the vehicle, such as the frame or axle mount. In such a mount, a torque plate is bolted to the caliper body and bolted to the fixed mounting member of the vehicle. The application of braking force to slow or stop the rotating rotor causes a transfer of torque from the rotor through the pads and to the caliper. The force is transferred through the caliper and torque plate to the mounting member. In this type of arrangement, the shear force is transferred through the bolts, which can cause the bolts to bend, even when large bolts are used. Bending of a bolt causes the caliper to twist, which results in many problems. A twisted caliper can cause uneven brake pad wear and uneven rotor wear, which can lead to thermal distortion of the rotor, cracking of the rotor and premature failure of the rotor. Twisting of the caliper can also lead to increased fluid displacement that can cause long pedal phenomenon in which a brake operator experiences a lengthened brake stroke and can also lead to a longer stopping distance. Twisting can also cause the piston carried by the caliper that actuates movement of the brake pads to become lodged in the piston bore.
Additionally, when the caliper needs to be removed and reinstalled, it is difficult to access and manipulate the large bolts needed to withstand the shear forces. This is especially true in cases of medium and heavy duty vehicles.
There is a need for a caliper and torque plate design that provides for a strong connection that has sufficient stiffness to withstand the shear force transferred during braking from a rotor through a caliper. There is also a need for simplified and easier removal and reinstallation of the caliper for service.